KR20030040617A - Water based Components for Over Printing Varnish - Google Patents

Abstract

PURPOSE: An aqueous over printing varnish(OPV) coating composition is provided, which shows excellent adhesive strength, gloss, heat resistance, moisture permeability and blocking resistance. CONSTITUTION: The aqueous over printing varnish coating composition comprises 100 parts by weight of the water-dispersive polyester copolymer represented by the formula 1; 1-45 parts by weight of an acryl copolymer; 1-45 parts by weight of a styrene copolymer; and 3-35 parts by weight of a water-soluble epoxy resin, wherein M is the group derived from a neutralizing agent; x and y are 0.1-0.6, respectively; and m+n is 1. Optionally the coating composition comprises further 3-10 parts by weight of an alcohol-based solvent; and/or 1-5 parts by weight of an antifoaming agent, a leveling agent or their mixture. Preferably the water-soluble epoxy resin is selected from the group consisting of dicarboxylic acid diglycidyl ether, neopentylglycol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythrol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, ethylene polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether.

Description

Water based Components for Over Printing Varnish

The present invention relates to an aqueous overprint varnish (OPV) coating composition, and more particularly, to include a water-dispersible copolyester, an acrylic copolymer, a styrene copolymer, a water-soluble epoxy resin, etc., thereby providing excellent coating properties and adhesion on a paper as a substrate. The present invention relates to an aqueous OPV coating composition having excellent surface gloss, heat resistance, moisture permeability, and blocking resistance.

Packaging refers to the technology and construction of suitable materials or containers on the goods in order to protect their value and condition in the transport and storage of the goods, and to the protection, integrity and convenience. Selecting and using appropriate packaging materials is necessary because it requires sales promotion, information and commu- nication, and environmentally-friendly.

Among these packaging materials, OPV is coated on the outer surface of various containers using paper, and is widely used for packaging of industrial products, cosmetics, or food. In particular, OPV used in food packaging containers should consist of ingredients that do not harm the human body.

Conventional techniques related to barrier coating or over coating compositions used in the packaging industry are as follows.

U.S. Patent No. 4,129,547 cures urea formaldehyde and low molecular weight polyhydric alcohols, and uses water-soluble emulsions of polyamides, polystyrenes, polyesters, and polyvinylidene as in U.S. Patent No. 4,804,573, for example using water-soluble polymers. Cold seals were performed, and US Pat. Nos. 5,008,144 and 5,035,946 used a varnish of water soluble polyethylene oxide. There is also a mixture of alkyl acrylate monomers acting as plasticizers, curing agents and water-soluble acrylic acids, as in US Pat. No. 5,616,364, and oxazolines or oxazines as in US Pat. Nos. 6,663,885 and 6,084,023. There is a composition using the contained methacrylate and UV curable overprinting composition which is 100% solids as in US Pat. No. 6,096,384. The coating and coating on the outer surface of the packaging container provides functional beauty and protects the contents. Emphasis was placed on non-stick properties.

As mentioned above, OPV is generally divided into oil-based using a polar organic solvent as a solvent, water-based aqueous and UV-curable 100% solids.

The conventional OPV coating composition using polystyrene or vinyl acetate uses a polar organic solvent such as toluene as a solvent, so that the organic solvent evaporates during the work, causing a change in viscosity resulting in uneven coating, and the working environment is exposed to a polar organic solvent. When the polar organic solvent is used in the packaging material, the health of the worker is impaired, and the residual solvent which may harm the human body is absorbed by the human body, thereby deteriorating the health. In contrast, aqueous OPV has several advantages over other types of OPV in terms of conservation of the environment, resource saving, improvement of working environment, and safety hygiene. Poor coating workability is poor, and water with a large latent heat of evaporation is difficult to volatilize, and thus flow is easily generated during drying. In addition, there is a problem that the water resistance is insufficient because the influence on the moisture in the atmosphere after the film is formed.

As a water-resistant complementary technique of the OPV composition using a conventional polyester, there is an example of curing polyester and melamine made by using less than 30% volatile solvent and polyhydric alcohol in US Patent No. 4,040,995. In US Pat. No. 4,054,614, there is an example where the side chain hydroxy group is cured with phthalic hydride after reacting pentaerythrol, a polyhydric alcohol, with an acid, thereby improving chemical resistance, hardness, and flexibility. In addition, in US Pat. No. 4,181,638, there is an example of forming a coating film by curing with a thermosetting agent using a polyester having a hydroxyl group in the side chain. However, the above patents have a problem in forming a film that is too strong according to the curing conditions to be used in a flexible substrate.

Accordingly, the present inventors have developed an aqueous OPV coating composition excellent in high gloss and water resistance by improving the above problems.

In particular, OPV required for food packaging is important for safety and hygiene. When used as food packaging bags and snack packaging materials, it does not harm any human body by removing residual solvents that are harmful to humans. Therefore, polar organic solvents such as toluene are released during coating. It should be removed to improve the working environment and have good wettability and dryness for the cardboard. It is also intended to meet the following performance required as an overprinting coating composition.

① Good coating workability, there should be no pinhole, brushing, catering, misting thread, etc., and there should be little viscosity increase during coating.

② It should be dry and have no blocking.

③ Good adhesion to the material (paper), so there should be no scratches, cracks or falling off during the process.

④ Do not bleed or discolor the ink, or create blemishes, separations, embossing, etc.

⑤ When used for food packaging, it should not give smell to foreign food or impair the taste of food.

⑥ The coated film should have less yellowing and gloss.

⑦ The storage stability of the coating composition should be good.

⑧ It must be economical.

In order to satisfy the above properties, water-disperse copolyester having excellent film forming ability is used, and an acrylic copolymer and styrene copolymer in the form of emulsion are added thereto to provide excellent coating property and adhesion on the substrate paper, and also wear resistance, The present invention has been completed by developing a composition having excellent surface gloss, heat resistance, durability, weather resistance, and the like.

Accordingly, an object of the present invention is to provide an aqueous OPV coating composition having excellent high gloss and water resistance composed of a water dispersion copolymer polyester, an acrylic copolymer, a styrene copolymer, and a water-soluble epoxy resin.

The present invention features an aqueous OPV coating composition composed of a water dispersion copolyester, an acrylic copolymer, a styrene copolymer, and a water soluble epoxy resin.

Referring to the present invention in more detail as follows.

In order to achieve the object of the present invention as described above, a water-dispersed polyester is used as a binder of an aqueous composition which can maintain a suitable viscosity for coating and can maintain good coatability and gloss and water resistance after coating. The general thermoplastic polyester starts with stretching the polyethylene terephthalate (PET) film produced by the polycondensation reaction of a divalent or higher alcohol and a divalent or higher carboxylic acid, and shows its strength. The biaxially stretched film has transparency and impact. It has been widely used as a representative packaging film with excellent bending and dimensional stability, and the demand for PET bottles for drinking water is expanding. However, in the non-stretched, there is a problem in moldability, impact resistance, and heat resistance, and in the present invention, in order to compensate for this, an acrylic copolymer and a styrene copolymer in the form of an aqueous dispersion or an emulsion are used.

The water-dispersed copolymer polyester used in the present invention has the structure shown in the following formula (1).

In Formula 1, M is a group derived from a neutralizing agent, x, y, m and n represent the composition ratio of each monomer, x and y are each in the range of 0.1 to 0.6, m + n = 1 .

The aqueous dispersion can be made in the form of a water-soluble or semi-soluble semi-dispersed solution using a neutralizing agent and water after most of them dissolve the resin synthesized using a water-soluble solvent as a solvent. When a large amount of hydrophilic groups are present in the polymer skeleton, the water resistance of the dry coating becomes very weak. Therefore, the water-dispersed copolyester of the present invention is a low molecular weight basic neutralizing agent, which greatly improves the dissociation polarity of the hydrophilic ions, thereby making it a relatively small amount of hydrophilic group. Solubilization is possible and the neutralizing agent is evaporated in the film formation process to form a film with excellent water resistance. Metal salts such as lithium, potassium, sodium and the like can also be used as neutralizing agents, but remain dry in the film even after drying, making the water resistance very weak. Accordingly, the low molecular weight basic neutralizers include ammonia, morpholine, dimethylamine, dimethyl ethylamine, triethylamine, N, N-dimethylamino ethanol, 2-amino-2-methyl propanol, monoethanol amine, diethanol amine , Diethylmethanol amine and triethanol amine are used to neutralize the water dispersion copolymer polyester. After blending the water-dispersed copolymer polyester having the molecular weight of 5,000 to 8,000 with the above structure of 10,000 to 15,000 in a predetermined ratio, and mixing and coating with the selected emulsion-type acrylic copolymer and styrene copolymer, it is dried and calendered. It is possible to form a film having good light.

In addition, in order to complement the physical properties of the water-dispersed copolymer polyester of the present invention, a good compatibility with the water-dispersed copolymer polyester is an acrylic copolymer, acrylonitrile, methyl methacrylate, ethyl having an appropriate molecular weight Emulsion-based homopolymers or copolymers based on methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate and butyl acrylate can be variously applied. The acrylic polymer homopolymer physical properties used in the present invention are summarized in Table 1 below.

The physical properties according to the molecular weight of the acrylic copolymer used for aqueousization were as shown in Table 2 below.

The acrylic copolymer used in the present invention can be represented by the following formula (2). At this time, the content of the acrylic copolymer used should be at least the minimum amount of blending well without phase separation with the water-dispersed copolymer polyester, it is preferable to use 1 to 45 parts by weight based on 100 parts by weight of the solid content of the water-dispersed copolymer polyester.

In Formula 2, R and R 'is a hydrogen atom or CH ₃ , R "is a hydrogen atom, CH ₂ CH ₃ or (CH ₂ ) ₃ CH _3dlrh , m, n represents the composition ratio of each monomer m + n = 1

As the styrene copolymer used in the present invention, α-methyl styrene and styrene-based emulsion-type homopolymers or copolymers can be used. In this case, since the content of the styrene copolymer should be at least the minimum amount that is well blended without phase separation with the water-dispersed copolymer polyester, 1 to 45 parts by weight based on 100 parts by weight of the solid content of the water-dispersed copolymer polyester.

In order to obtain better gloss, the aqueous OPV is coated and then calendered as necessary. Calendering is a means mainly applied for the purpose of improving the surface quality by improving not only the uniformity of thickness but also the smoothness and gloss of the surface. Although calendaring improves coating surface properties such as smoothness and gloss, optical properties such as transparency and stiffness and some strength properties may be worsened depending on the conditions. Therefore, during hot calendering, the coating layer should be fused to form a leveling, so that the adhesion to the cardboard should be excellent, and the film against heat fusion should not age or stick to the calendering plate. For good release force without tacky against hot calender surfaces, the coating of the aqueous overcoating layer must be strengthened. To this end, it has a cross-linkable functional group that can form a partially interpenetrating polymer network structure between the water-disperse copolyester and the acrylic copolymer. Can complement. In particular, preferably dicarboxylic acid diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether Film by using water-soluble epoxy resins such as diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, ethylene polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether Can increase the strength.

At this time, the content of the water-soluble epoxy resin used should be at least a minimum amount to prevent the coating surface from sticking by the calendering roll heat, and if used excessively, the flexibility of the film may be deteriorated and cracks may occur, thereby degrading physical properties. 3-35 weight part is preferable with respect to 100 weight part of solid content of water dispersion copolymer polyester.

In addition to such compositions, alcohols, fillers, antifoaming agents, leveling agents and the like can be used as additives.

Environmental issues and workability Ethanol, isopropyl alcohol, butanol, ethylene glycol, isopropyl glycol, ethyl glycol, butyl glycol, propylene glycol, 1-methoxy-2-propanol, 1 Alcohol solvents such as ethoxy-2propanol, 1-propoxy-2-propanol, and 1-butoxy-2-propanol within 3 to 10 parts by weight based on 100 parts by weight of solids of the water-dispersed copolyester. Can be used.

In addition, organic and inorganic fillers may be used to impart antiblocking, slippage and surface feeling. Organic materials include polyethylene, polypropylene, polystyrene, polyacrylate, modified starch, and oxidized starch particles. Inorganic substances include calcium carbonate, kaolin, clay, zinc oxide, titanium oxide, barium sulfate, alumina, silica and the like. Since a large amount of this filler can reduce the gloss of the coating layer, it is preferable to use about 0.1 to 20 parts by weight with respect to 100 parts by weight of the solid content of the water-dispersed copolyester, and a particle size of 1 to 60 µm is preferable. .

On the other hand, during surface defects of the coating surface, the surface to be coated has foreign substances such as water, oil, silicone, etc., resulting in cratering (a phenomenon in which irregularities such as craters are formed on the coated surface), fisheye, pinhole, and orange peel phenomenon. It is preferable to use 1 to 2 parts by weight of the mixture of the surfactant with respect to 100 parts by weight of the solids of the water-dispersed copolyester to remove or reduce the amount and to promote excellent gloss and smoothness of the high coating surface.

In addition, an antifoaming agent, a leveling agent or a mixture thereof may be added, and these are generally used, but in particular, the antifoaming agent may be anionic, cationic or silicone type, and the leveling agent may be polydimethylsiloxane, polymethylalkylsiloxane, Polyether modified polydimethylsiloxane, polymethylalkylsiloxane, etc. are preferable, and it is preferable to use 1-5 weight part with respect to 100 weight part of solid content of water-dispersion copolymerization polyester. At this time. If it is out of this range, there is a problem that the physical properties of the surface deteriorate to the surface.

Hereinafter, the present invention will be described in detail based on the following examples, but the present invention is not limited thereto.

Example 1

The following composition was coated on a basis weight 350 g / m ² cardboard using a bar coater and then dried in an oven (90 ° C., 30 seconds) to give a coating amount of about 10 g / m ² .

100 parts by weight of water-dispersed copolymer polyester [SK Chemical EW 312, solid content 30%]

7.5 parts by weight of acrylic copolymer [Samyoung Ink KP430 KS, solid content 28%]

11.25 parts by weight of styrene copolymer [Hanhwa Petrochemical HG-80, solid content 30%]

8 parts by weight of water-soluble epoxy resin [Nagase DENACOL EX-810, solid content 25%]

Antifoaming agent [BYK-Chemie 053] 1.25 parts by weight

Example 2

Coating was carried out in the same manner as in Example 1 except that the coating composition of the coating layer was carried out as follows.

100 parts by weight of water-dispersed copolymer polyester [SK Chemical EW 312, solid content 30%]

6.25 parts by weight of acrylic copolymer [Samyoung Ink KP430 KS, solid content 28%]

6.25 parts by weight of styrene copolymer [Hanhwa Petrochemical HG-80, solid content 30%]

6.25 parts by weight of water-soluble epoxy resin [Nagase DENACOL EX-313, 25% solids]

6.25 parts by weight of ethanol

Example 3

Coating was carried out in the same manner as in Example 1 except that the coating composition of the coating layer was carried out as follows.

100 parts by weight of water-dispersed copolymer polyester [SK Chemical EW 312, solid content 30%]

21.5 parts by weight of acrylic copolymer [Samyoung Ink KP430 KS, solid content 28%]

14.5 parts by weight of styrene copolymer [Hanhwa Petrochemical HG-80, solid content 30%]

7.5 parts by weight of water-soluble epoxy resin [25% of Japan Nagase DENACOL EX-512]

Comparative Example 1

The following composition was coated on a basis weight 350 g / m ² cardboard using a bar coater and then dried in an oven (90 ° C., 30 seconds) to give a coating amount of about 10 g / m ² .

100 parts by weight of water-dispersed copolymer polyester [SK Chemical EW 312, solid content 30%]

7.5 parts by weight of acrylic copolymer [Samyoung Ink KP430 KS, solid content 28%]

11.25 parts by weight of styrene copolymer [Hanhwa Petrochemical HG-80, solid content 30%]

Antifoaming agent [BYK-Chemie 053] 1.25 parts by weight

Comparative Example 2

Coating was carried out in the same manner as in Comparative Example 1 except that the coating composition of the coating layer was carried out as follows.

100 parts by weight of water-dispersed copolymer polyester [SK Chemical EW 312, solid content 30%]

6.25 parts by weight of acrylic copolymer [Samyoung Ink KP430 KS, solid content 28%]

6.25 parts by weight of styrene copolymer [Hanhwa Petrochemical HG-80, solid content 30%]

6.25 parts by weight of ethanol

Comparative Example 3

Coating was carried out in the same manner as in Comparative Example 1 except that the coating composition of the coating layer was carried out as follows.

100 parts by weight of water-dispersed copolymer polyester [SK Chemical EW 312, solid content 30%]

21.5 parts by weight of acrylic copolymer [Samyoung Ink KP430 KS, solid content 28%]

14.5 parts by weight of styrene copolymer [Hanhwa Petrochemical HG-80, solid content 30%]

Comparative Example 4

Coating was carried out in the same manner as in Comparative Example 1 except that the coating composition of the coating layer was carried out as follows.

Polystyrene 30% by weight

Toluene 69 wt%

Antifoam 1 wt%

The evaluation of the coating amount, glossiness, moisture permeability, and adhesion according to Examples 1 to 3 and Comparative Examples 1 to 4 is summarized in Table 3 below.

Test Example

[Measurement of physical properties]

1. Glossiness

Comparative Example 4 was calendered at a pressure of 150 kgf / m ² at 100 ° C., and the rest of the Examples and Comparative Examples were measured with Tri microgross 160 [Sheen] and measured 60 degrees of glossiness 10 times. Compared to.

2. Breathability (KS A 1013)

The amount of moisture absorbed for 24 hours per 1 m ² by using anhydrous calcium chloride as an absorbent and placing it in a constant temperature and humidity device with a humidity of 90 ± 2% and a temperature of 40 ± 1 ℃. The water vapor transmission rate was measured in terms of.

3. Adhesion Measurement

100 squares were formed in a 2.5 cm square on the coated substrate and attached to a tape and measured by the number of squares removed after peeling.

4. Blocking resistance measurement (KS A 1024)

It is to check the degree of tearing of the coating layer by the pressure, temperature and humidity of the coated surface is to test the problems that may occur when the packaging is stacked after packaging. After contacting the coated and non-coated surfaces for 24 hours at a humidity of 75%, a temperature of 40 ± 1 ℃, a weight of 45 × 30 mm 500 g, and a pressure of 10 kgf / m ² , each surface is torn when the contact surface is removed. The degree of visual evaluation was visually evaluated and evaluated in three steps.

There is no blocking (◎) There is some blocking (△) There is blocking (×)

As described above, in the case where the coating was made constant and the coating film was cured using a water-soluble epoxy resin as a result of calendering at a pressure of 150 kgf / m ² at 80 ° C., the coating film was high in gloss. In the comparative examples (1, 2, 3) that were not cured, it was found that the heat resistance of the film was poor and the film was aged by high temperature calendering and the gloss was deteriorated. Since the glass ion of the polystyrene itself of Comparative Example 4 was 100 ° C., the gloss was alive without any influence in the calendering process. In addition, the present invention was found to have a property that can maintain excellent gloss even when calendering at a lower temperature than conventional oil-based products.

In the case of moisture permeability, the physical properties of the coating surface are densified in Examples 1 to 3 in which the coating film is cured, and the moisture permeability is much lower than that of Comparative Examples 1 to 3.

In the case of the adhesive force, the Example has high flexibility and shows excellent adhesiveness, but as shown in Comparative Example 4, it was found that the flexural adhesive strength was lowered due to the stiffness of the polymer itself.

In the case of blocking resistance, it was found that the examples had no blocking.

However, in the case of Comparative Example 4, the moisture permeability and blocking resistance were better than the example, but there is a problem that harms the health by absorbing the body as well as polluting the environment by using harmful organic solvents such as toluene, the present invention In the case according to the embodiment has excellent coating adhesion and gloss, moisture permeability and blocking resistance, has the advantages of environmental conservation and harmless to the human body.

As described above, the coating composition according to the present invention has excellent coating properties on the paper as a substrate due to the partial crosslinking reaction properties of the acrylic polymer and the water-soluble epoxy polymer in various emulsion forms with the excellent film forming ability and glossiness of the water-dispersed copolymer. It is possible to provide a composition which exhibits excellent adhesiveness and heat resistance, excellent surface gloss, heat resistance, moisture permeability and blocking property. In addition, it preserves the environment, such as improving the workplace and has an advantage in terms of safety hygiene.

Claims (5)

Aqueous OPV, comprising 100 parts by weight of water-dispersed copolymer polyester having a structure as shown in Formula 1, 1 to 45 parts by weight of acrylic copolymer, 1 to 45 parts by weight of styrene copolymer, and 3 to 35 parts by weight of water-soluble epoxy resin. (Over Printing Varnish) Coating Composition. Formula 1 In Formula 1, M is a group derived from a neutralizing agent, x, y, m and n represent the composition ratio of each monomer, x and y are each in the range of 0.1 to 0.6, m + n = 1 . The method of claim 1, wherein the water-soluble epoxy resin is dicarboxylic acid diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythrol Polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, ethylene polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether An aqueous OPV coating composition. The method of claim 1, wherein M is ammonia, morpholine, dimethylamine, dimethyl ethylamine, triethylamine, N, N-dimethylamino ethanol, 2-amino-2-methyl propanol, monoethanol amine, diethanol amine, Aqueous OPV coating composition, characterized in that a group derived from a basic neutralizing agent selected from diethylmethanol amine, triethanol amine. The composition of claim 1, wherein the composition comprises ethanol, isopropyl alcohol, butanol, ethylene glycol, isopropyl glycol, ethyl glycol, butyl glycol, propylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2propanol, Aqueous OPV coating, characterized in that 3 to 10 parts by weight of an alcohol-based solvent selected from 1-propoxy-2-propanol and 1-butoxy-2-propanol is added to 100 parts by weight of solids of the water-dispersed copolymer. Composition. The aqueous OPV coating composition according to claim 1, wherein 1 to 5 parts by weight of an antifoaming agent, a leveling agent or a mixture thereof is added to 100 parts by weight of the solid content of the water-dispersed copolyester.